AC voltmeter using pic16f877a and LCD

[sunny]

Hi Alll...
i am going to make an AC volt meter using pic and lcd...
almost all the design and software is ready and working conditions under here...
that meter takes from 0 to 5 V DC.
if there is 2.5 V then meter shows reading of 250 volts and if there is 4.2V DC then meter shows 420V AC.... and so forth...
problem is that how to convert AC 220 volts into 2.2 volt DC...
and this converting circuit should be so sensitive that takes 231V ac and converts them in 2.31V DC...
i used resistor voltage divider network...
100K + 1K on 220 volts...it gives 2 volts across 1K but that not works well, because a minor change in 220V makes my reading so far...
so give me some solution.
request to alllll.

[orpheedulogis]

I think you will have many problems if you try directly use 220V

First it would be better you use complete isolation between PIC solution and 220V (not same ground)
Second it's quite difficult to do good ADC conversion: you need perfect regulators, correct PCB ... even if you do this, you will see PIC will give you different value and you have to make software approximations.

For ADC I use LT1990. The advantage is that inputs are isolated.

[sahu]

i think he want ADC calculation .i want also ..

[sahu]

right now i use it calculation but display wrong value ..

ADC_Value = ADC_Read(2);

DisplayVolt = ADC_Value * 2;

volt[0] = DisplayVolt/1000 + 48;

volt[1] = (DisplayVolt/100)%10 + 48;

volt[3] = (DisplayVolt/10)%10 + 48;
volt[4] = (DisplayVolt/1)%10 + 48;

[sunny]

thanks forreplay
my next questions in not related to this topic but replay must....
in what range of frequency we cn generate using pic